bug#27552: 25.2.50; Indentation problem in rnc-mode

[Ivan Andrus]

The RNC snippet below (from
http://cs.brown.edu/courses/cs196-9/slidestore/relaxng.html) shows an
indentation problem when using multiple opening namespace/datatypes
clauses.

-Ivan

default namespace rng = "http://relaxng.org/ns/structure/1.0";
                            namespace local = ""
                                                  datatypes xsd = 
"http://www.w3.org/2001/XMLSchema-datatypes";

start = pattern

pattern =
    element element { (nameQName | nameClass), (common & pattern+) }
    | element attribute { (nameQName | nameClass), (common & pattern?) }
    | element group|interleave|choice|optional
              |zeroOrMore|oneOrMore|list|mixed { common & pattern+ }
    | element ref|parentRef { nameNCName, common }
    | element empty|notAllowed|text { common }
    | element data { type, param*, (common & exceptPattern?) }
    | element value { commonAttributes, type?, xsd:string }
    | element externalRef { href, common }
    | element grammar { common & grammarContent* }



In GNU Emacs 25.2.50.5 (x86_64-apple-darwin15.6.0, NS appkit-1404.47 Version 
10.11.6 (Build 15G1421))
of 2017-06-28 built on iandrus-osx
Repository revision: efe7a7f79f8eb9c716136561821d350b69456b55
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
'configure --without-makeinfo PKG_CONFIG_PATH=/opt/X11/lib/pkgconfig'

Configured features:
JPEG RSVG DBUS NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: RNC

Minor modes in effect:
  achievements-mode: t
  highlight-symbol-mode: t
  which-function-mode: t
  show-paren-mode: t
  global-semantic-stickyfunc-mode: t
  save-place-mode: t
  msb-mode: t
  minibuffer-depth-indicate-mode: t
  gud-tooltip-mode: t
  global-hl-line-mode: t
  delete-selection-mode: t
  guide-key-mode: t
  auto-insert-mode: t
  yas-global-mode: t
  yas-minor-mode: t
  ido-everywhere: t
  beacon-mode: t
  global-page-break-lines-mode: t
  gvol-mode: t
  diff-auto-refine-mode: t
  magit-auto-revert-mode: t
  global-auto-revert-mode: t
  global-git-commit-mode: t
  async-bytecomp-package-mode: t
  shell-dirtrack-mode: t
  TeX-PDF-mode: t
  global-edit-server-edit-mode: t
  auto-image-file-mode: t
  desktop-save-mode: t
  drag-stuff-global-mode: t
  drag-stuff-mode: t
  recentf-mode: t
  global-anzu-mode: t
  anzu-mode: t
  keyfreq-autosave-mode: t
  keyfreq-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t